The present invention relates to pigments which can be used in a variety of applications, and more particularly relates to the modification of pigments to improve various properties.
Pigments have been used in a variety of applications, such as in inks, coatings, toners, plastics, rubber, films, and the like. Common goals in each of these applications are to provide a pigment which is capable of being substantially and uniformly dispersed, and capable of remaining dispersed in the composition so that color and other properties exhibited by the pigment are uniform throughout the composition or material which incorporates the pigment. The improvement in the dispersibility and dispersion stability of pigments has been attempted previously and has included coating or adsorbing various surfactants onto the pigment. However, merely adsorbing or coating pigments had potentially several disadvantages. First, adsorbed surfactants are dependent on the physical properties of the surrounding materials, such as the solvent with the ink. In such a situation, an equilibrium may exist between the surface of the pigment and the solvent for surfactant affinity. Solubility issues involving the surfactant and the solvent may also come into effect. Other considerations which can effect adsorbed surfactants are the concentration of the pigment, the type of surfactants used, and the temperature and pH of the composition or material containing the pigment. Any one or more of these physical properties can cause the removal of the surfactant from the surface of the pigment and create additional surfactant in the bulk liquid or medium which may negatively effect the dispersion stability and other properties of the bulk liquid such as foaming, surface tension, viscosity, film strength, film elasticity, and the like. In addition, the excess surfactant which may be found in conventional pigments may also be detrimental to plastic or film-forming properties, such as color, strength, elongation, elasticity, and the like. Accordingly, there is a desire in the art to improve the dispersibility and dispersion stability of pigments with respect to overcoming one or more of the above-described disadvantages.